EFEITO DO MANEJO E DE VARIÁVEIS BIOCLIMÁTICAS SOBRE A TAXA DE GESTAÇÃO EM VACAS RECEPTORAS DE EMBRIÕES

Abstract

This work aimed to verify the effects of the handling andthermal environment on the pregnancy rate of embryo-recipientzebu x European cows (n=94) as well as the behavioral and clinicalaspects at the moment of embryo transfer. Cortisol was analyzed byplasmatic samplers collected on D0, D9 and D16 of the hormonaltreatment for estrous synchronization; blood was also sampled toanalyze progesterone levels at the moment of embryo transfer.There was no difference (p>0.05) between pregnant and notpregnant females for maturation stage and embryo classification,coat, and reactivity between fresh and frozen embryos. Thecortisol concentrations decreased (p>0.001) between D0 and D16,and the concentration of progesterone was similar in function ofthe pregnancy stage. Nevertheless progesterone in D16 for nonpregnant cows was lower than for pregnant ones in the same day.Moreover, pregnant cows showed lower skin temperature. Thevalues of Black Globe-Humidity Index were at very high limits,indicating that all animals could be under heat stress. The regressionanalysis indicated a tendency (p=0.08) to increase the pregnancyprobability of 25% between the beginning and end of the afternoon.Thus, low plasmatic concentration of progesterone and high skintemperature represents a factor of thermal discomfort at the momentof the embryo receiving, influencing the pregnancy rate of recipientcows. As observed, heat stress decreased the probability of thepregnancy of recipient cows in tropical environment.

Keywords

• Beef cattle
• cortisol
• handling
• heat stress
• pregnancy rate